Stressed metal technology has been adapted to fabricate interconnects between small components in a circuit. One example of a common interconnect is a flip-chip interconnect that connects a circuit board to an integrated circuit. These interconnects are usually either mechanically pressed against a circuit board pad or soldered into a circuit board pad.
One problem with such interconnects is that differential rates of thermal expansion between the integrated circuit and the circuit board moves the ends of the interconnects. A mechanical pressed contact can accommodate some of the stresses by sliding over its mating circuit board pad. A soldered contact in which the ends are fixed typically relies on the in-plane spring compliance to handle the movements. However, conventional straight stressed-metal springs, although flexible along their axis, have a rather limited compliance for stresses in a lateral direction, a direction that is perpendicular to the axis of the stressed metal spring.
In response, J-Shaped spring contacts have been developed as described in U.S. patent application Ser. No. 10/443,957, entitled “Multi-Axis Compliance Spring” based on provisional application No. 60/382,602 filed May 24, 2002. The entire document of the patent application and the related provisional application are hereby incorporated by referenced in their entirety. Although the disclosed J spring designs offer improved lateral compliance, the designs use substantial area on an integrated circuit. Furthermore, the design of the J springs make it difficult to route traces around the spring array. Additionally, in J springs that include bends exceeding 90°, the contact point that mates with the circuit board pad, is not the spring tip but rather the J spring outer edge. When the approximately 90 degree point of the outer edge is soldered to the mating board pad, extending the J shape beyond 90° does not provide additional spring compliance.
Thus an improved system that offers enhanced lateral compliance to make interconnects between small circuit elements is needed.